I was wondering how to pass data between windows that are
opened by Adobe AIR.

In this application, the parent window opens another native
child window. The child window has some text under the DIV section.
If the child window is already opened, the parent window should
just pass the data to the child window and the child window
displays the data.

Also I want to trigger an event in the parent window from the
child window and a data passed from the child window. How do we do
this?

To get to the JavaScript window object of the child, use
newWindow.window.

createRootWindow() doesn't set a reference to the parent on
the child window (hence the "root" in the function name), but you
can set it yourself after loading the content. Just set the child
parent and opener properties in an event listener for the complete
event: